m 
173 
«I have arrived at completely similar results from my study of 
Asterina gibbosa. The existence of a sinus surrounding the stone-canal 
‘throughout its whole course from the ringcanal to the madreporic 
Fig. 1b. 
_ madreporic pore 
stone canal ..........}l.......B ER “genital rachis 
sinus Of Y 
(aboralsinus) __ 
SIRUSICHT A EL NE 
(wxlal sinus) 
plate, is well known, as is also the fact that besides the stone canal, 
a glandular organ, the so-called heart, is likewise contained in it. 
If we make two sections of the sinus and its contained organs in 
a young Asterina about 1 mm, in diameter, one about the middle of its 
course and the other, in 
the region of the madre- Fig. 2a. 
poric plate, we get the 
appearances represented 
in Figs. 2a and 2d respec- 
tively. In figure 2a we 
see that the dorsal organ STI > 
consists of an inwardly 
directed fold, covered on 
the outside by the epithelium which lines the axial sinus (called sinus 
c for reasons which will immediately appear). In the interior of this 
fold, we have a mass of rounded cells staining brown with osmic acid. 
In order to avoid too many figures, in 25 I have represented appea- 
rances in the same section, which are usually only seen in successive 
sections through the madreporite. We see now that the stone-canal 
communicates with the axial sinus, and that the dorsal organ is re- 
presented at this level by atube lined with a well definedepithe- 
lium. This tube we shall call sinus 3. Further down towards the 
mouth its lumen becomes virtual and it is represented by a solid cord 
of cells. Further we see that from the one corner of this tube, there 
WE... anterradial fold 
of body wall. 
N[......sinus c (axial sinus) 
N U... dorsal organ 
